This invention relates to a bearing device of a sealed type scroll compressor.
In a sealed type scroll compressor, an orbiting scroll member is maintained in meshing engagement with a fixed scroll member and driven for orbiting movement with respect to the fixed scroll member by means of a crankshaft without apparently rotating on its own axis, to cause a fluid in a sealed space defined between the two scroll members to perform a pumping action.
In this type of sealed type scroll compressor, the crankshaft includes a crank section engaging the orbiting scroll member and a shaft section supported by a frame. The support structure for the crankshaft can be broadly divided into two types: one type is in the form of plain bearings and the other type is in the form of roller bearings. One example of the support structure of the plain bearing type is described in Japanese Patent Publication No. 76201/82 and comprises a first plain bearing mounted on the orbiting scroll member and engaging the crank section of the crankshaft, and a second plain bearing and a third plain bearing mounted on the frame for supporting the shaft section of the crankshaft. In this type of support structure comprising plain bearings, the crankshaft is tilted by the action of the pressure of a fluid in the sealed space defined between the two scroll members within the range of a gap existing between the crankshaft and the plain bearings and strongly forced against the respective bearings. Thus, the crankshaft has tended to exert on each bearing a force which is not symmetrically applied to each bearing, so that one end of the bearing should bear a higher force than the opposite end, causing an increase in a bearing friction loss. Moreover, the reaction of the oil film provided by the one end of the bearing has not been sufficiently high to avoid wear caused on the bearing and a seizure which occurs in the bearing, and the bearing gap between the plain bearing and the crankshaft has become wedge-shaped in cross section due to the application of unsymmetrical pressure to the bearings. Owing to this phenomenon, the sealed type scroll compressor has suffered the disadvantage that a gaseous refrigerant incorporated in the lubricant stays in the bearing gap of the wedge shape and reduces the viscosity of the lubricant in the bearing gap, thereby causing wear and seizure on the bearing.